The Occum Hydroelectric Plant and Dam is a historic hydroelectric plant and dam north of Bridge Street on the west side of the Shetucket River in Norwich, Connecticut. It masonry-concrete dam was built in 1865. It stands 14 feet high, and impounds a maximum of 600 acre-feet of water. The city of Norwich's Department of Public Utilities owns the site, which was added to the National Register of Historic Places in 1996. The dam was originally built to provide water power to mills located downstream (a use that continued in one mill complex until 1980), and was adapted for electric power generation with the construction of the brick powerhouse in 1934. It is one of a small number of surviving hydroelectric plants in the state which was built before 1940.